Abstract
Abstract The vascular wilting caused by Fusarium oxysporum f. sp. dianthi (Fod) is the most relevant disease for carnation cultivation. Understanding the biochemical mechanisms involved in resistance to Fod will allow the development of new disease control strategies. In this research, the levels of some phytohormones such as salicylic acid (SA), methyl salicylate (MeSA), and methyl jasmonate (MeJA) were evaluated in symplast of carnation roots infected with this pathogen. The accumulation of these hormones was then correlated with the expression levels of symplastic peroxidases, enzymes involved in the plant resistance against pathogen during interaction. Our results suggested that pathogen infection causes a differential accumulation of SA, MeSA, and MeJA in a resistant cultivar (i.e. ‘Golem’), being earlier and higher than that observed in a susceptible one (i.e. ‘Solex’). Simultaneously, an increase of guaiacol peroxidase enzymatic activity (GPX) and transcriptional levels of a gene coding for a symplastic peroxidase were presented as part of the resistance response. The positive statistical correlation between the accumulation of SA and MeJA and the expression of peroxidases (GPX activity and mRNA levels) indicates the possible cellular relationship of these phenomena during the activation of the resistance to Fod. Our findings suggested some hormonal signaling mechanisms acting at the roots during the regulation of the biochemical response associated with resistance against Fod.
Highlights
Carnation is a herbaceous plant that belongs to the family Caryophyllaceae and the Dianthus genus (Hernandez, 1983)
An important condition to point out is related to the testing time employed in this study in order to observe the biochemical responses, since such an evaluation was carried out up to a maximum of 14 days after inoculation, during which time the plants were healthy and vigorous
This sequential accumulation is likely presented by the activation of salicylic acid carboxyl methyltransferase (SAMT), which has been reported to play an important role in the activation of resistance responses in the plant, such as Systemic Acquired Resistance
Summary
Carnation is a herbaceous plant that belongs to the family Caryophyllaceae and the Dianthus genus (Hernandez, 1983). The lignin accumulation and the regulation of highly oxidizing species are determining mechanisms of resistance to vascular pathogens. In this sense, peroxidase enzymes play a determining role since their participation in this type of phenomenon has been widely reported and discussed (Hakeem et al, 2014; Prakasha and Umesha, 2016). An increase of the activity levels of guaiacol peroxidase (GPX) has been reported as an important response against Fusarium pathogens (Cuervo et al, 2009; Anthony et al, 2017), including the causal pathogen of carnation vascular wilting, i.e., Fod (Cuervo et al, 2009; Ardila et al, 2011 Ardila et al, 2014). The regulatory mechanisms related to the expression of this enzyme and the signaling molecules involved in these biochemical responses are not previously described
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